Align HfFileSystem and HfApi for the expand argument when listing files in repos

[lhoestq]

HfAPi has it set to False by default, so should HfFileSystem. In this PR I set it to False by default for HfFileSystem.

This will be particularly useful for pyarrow 21.0 when it comes out. Currently having expand=True by default causes issues because it's an expensive operation:

In [1]: import pyarrow.dataset as ds
   ...: 
   ...: uri = "hf://datasets/HuggingFaceFW/fineweb-2"
   ...: dataset = ds.dataset(uri)
HTTP Error 429 thrown while requesting GET https://huggingface.co/api/datasets/HuggingFaceFW/fineweb-2/tree/main?recursive=True&expand=True&cursor=ZXlKbWFXeGxYMjVo...
Retrying in 1s [Retry 1/20].
HTTP Error 429 thrown while requesting GET https://huggingface.co/api/datasets/HuggingFaceFW/fineweb-2/tree/main?recursive=True&expand=True&cursor=ZXlKbWFXeGxYMjVo...
Retrying in 1s [Retry 1/20].
...

This will make HfFileSystem more efficient overall :) (kinda related to #3177 )

[HuggingFaceDocBuilderDev]

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[Wauplin]

Changes makes sense and looks good, thanks! 👍 (hope it doesn't break things in the wild though 😬)

[lhoestq]

(hope it doesn't break things in the wild though 😬)

It's fine for all the other cases I know of: pandas, dask, spark, datasets.